1. Field of the Invention
The present invention pertains to the field of devices and methods that may be utilized in treating liquids for the removal of contaminants such as pathogens, and, more particularly, to portable biocide filters used to destroy bacterial and viral pathogens during the production of potable water.
2. Statement of the Problem
Hand-held water purification devices have been developed, primarily, for the benefit of travellers who are confronted with available water supplies of poor and dangerous quality. In many underdeveloped countries, the public water supply is not potable, and can carry severe or even life-threatening diseases, such as typhoid, cholera, hepatitis, and dysentery. Even pristine wilderness areas have water supplies that are increasingly contaminated with a variety of particulate matter including, insects, nematodes, fungi, algae, yeasts, and pathogenic microorganisms.
There are many pathogens in potential sources of drinking water, such as protozoa that can be removed by filtration. Bacteria can also be removed by proper filtration; however, filtering bacteria is difficult with a portable water filter. Viruses are extremely difficult to remove from drinking water by filtration, and it is impractical to filter viruses in a portable or hand-held water filter. Viral pathogens can be responsible for such diseases as hepatitis, poliomyelitis, and gastroenteritis or diarrhea derived from rotavirus. In use, the ultrafiltration devices that are required for the removal of viruses are often associated with vexatious clogging problems.
Hembree et al, U.S. Pat. No. 5,106,500, discloses a hand-held water filtration pump including a porous body of biocide formed of water-soluble halogenated anion-exchange resins. Water is first filtered through a mechanical filter, then forced under pressure through the porous biocide.
Hembree et al, U.S. Pat. No. 5,268,093, discloses a water filtration pump having a biocide-containing canister positioned to receive water from a mechanical filter. A chemical scavenging material may be positioned to receive water discharged from the biocide filter for the removal of chemicals from the water.
The prior hand-held biocide pump-filters are associated with critical difficulties pertaining to pressure drop across the biocide bed. A significant pressure drop occurs as the untreated water is passed through the packed bed of biocide material. This pressure drop demands the exertion of wearisome manual forces on the pump handle, and produces corresponding wear in the pump components.
Prior devices utilize relatively dense or impermeable biocide resin beds to increase surface area contact with the water and to prolong transit time through the bed for purposes of increasing dissolved biocide levels to effective amounts. Unfortunately, in use, the treatment process is often short-circuited by channeling and compaction of the biocide filter-bed material due to flow rates in excess of design limits on behalf of impatient users. These problems have burdened the prior types of biocide filter devices with bad reputations for difficulty in use and limited effectiveness against pathogens.
Despite prior efforts to develop a workable hand-held water purification apparatus for treating polluted water, there remains a heartfelt need to produce a compact, easy to use, effective device.